1. Field of the Invention
This invention relates to mass storage systems in general and, more particularly, to read channel data filters in mass storage systems.
2. Description of the Prior Art
The read channel in a mass storage system "demodulates" data read from a magnetic medium, such as a disk, and converts the demodulated data into a form which can be utilized by a computer, for example.
As will be explained in more detail below, the data recorded on the disk is preferably uniform in density, typically measured in bits per inch, to strive for the maximum data capacity that the disk can hold. A consequence of this is that the data read from (and, correspondingly, written to) the disk varies in frequency from the innermost tracks to the outermost tracks since the disk spins at a substantially constant rate.
To increase the reliability of the system, the error rate of the read data should be minimized. Since a mass storage system is similar to a conventional communication system, a filter is added to the read channel before demodulation to provide equalization and remove much of the noise in the read data. In a typical read channel, this filter is a low-pass filter whose characteristic frequency (cut-off frequency) is fixed to the frequency of the read data. However, this may not be the most optimal setting for the characteristic frequency of the filter, resulting in less than the maximum possible eye opening in the read data.
Thus, it is desirable to provide a read channel circuit having a filter that may be adjusted to provide the desired eye opening in the read data.